Over the past two decades, viral and non-viral vectors have emerged as potential delivery systems for cancer gene therapies (1-4). However, each system has a drawback in that biomedical application is limited. For gene therapies, various viral gene transfer systems such as adenoviruses (Ads), lentiviruses, retroviruses and adeno-associated viruses have been studied (5-7). Ads have several unique characteristics such as efficient infection, high loading capacity, and a lack of insertional mutagenesis. As a result, Ads are widely used as a potential anticancer therapy. However, gene transfer using Ads is limited due to dependency on a coxsackievirus and adenovirus receptor (CAR) for transduction (8).
Non-viral vectors have several advantages compared to viral vectors. The non-viral vectors cause low immune responses, have good reproducibility, and have a relatively simple quality control process. As potential, non-viral gene carriers, cationic polymers have been widely investigated. These cationic polymers include polyethylenimine (9-11), poly(amidoamine) (12-16), poly(amino ester) (17) and poly(L-lysine) (18-20).
However, a cationic polymer-based gene transfer system has a drawback of having lower transduction efficiency than a viral gene transfer system. Recently, numerous research on cell penetrating characteristics of cationic arginine (Arg) and Tat peptides having arginine residues have been conducted. Arginine residues can effectively deliver nucleic acids through intracellular translocation (21-24), which is probably caused by the membrane permeability of Arg moieties (25-27). Accordingly, research on modification of various cationic polymers such as chitosan (27), poly(amidoamide), dendrimers (28-31) with arginine residues have been conducted and showed that such polymers have significantly enhanced transduction efficiency compared to unmodified polymers.
In previous research, the inventors attempted to combine non-viral advantages to a viral vector. Accordingly, arginine-grafted, bioreducible polymer (ABP) was produced, and it was confirmed that an ABP and Ad complex (Ad/ABP) has enhanced transduction efficiency and decreased innate immune response, compared to naked Ad (32). However, the size of the complex vector was more than 500 nm which is larger than the ideal size for effective cellular uptake (32). The maximum size for effective cellular uptake through a non-specific, clathrin-dependent process is less than 200 nm.
Therefore, in order to solve such a conventional problem, there is a demand for developing a bioreducible polymer-virus complex which has a size that is less than 200 nm and can be applied in in vivo gene therapy.
Throughout the specification, references are made to numerous theses and patent literature, and citations are represented in parentheses. Disclosures of the cited theses and patent literature are incorporated in its entirety herein by reference to more clearly describe the standard of technology including the present invention and the scope of the present invention.